Cooling left side hotter than right
 

Hi, wondering if anyone has seen this before?
I have a 64 Catalina 389, rebuilt engine. runs hot, but has not boiled. Runs about 230F on warm days...say days above 80.. I put Holley Sniper EFI on the motor with a separate temp sensor and it reads about 20F cooler.
Using and IR type temperature gun, I found that the Right side of the engine runs about 20F warmer than the Left. I tried a Flowkooler pump... No difference. So then I got radical and modified the original pump so flow to the right side through the pump and plates so that it worked like the flow on the left side.. direct from the impeller... more like an 11 bolt pump... absolutely no difference to idle temp or balance...
I am running twin thermo fans, new 3 core copper (with closer tubes) radiator, tried both 180 and 160 thermostats..Engine has been fully rebuilt... 30 thou oversized.

Any ideas? I can mount the temp sensor in the top hose or radiator to get an "average" temperature, but of course thats past the thermsostat... and it doesnt solve the temperature imbalance which is my real concern since one side can overheat and I wouldn't know it..

All advice gratefully accepted.

Thanks